Swash-plate rotary engine



5, 1930. J. F. N. CRAIG I SWASH PLATE ROTARY ENGINE Filed Feb. 26, 1930Patented Aug. 5, 1930 unrrensmres P ENT lorries .rorrnrnnnnnicknnvmsonCRAIG, or 'BRoxBoURnn, ENGLAND s Asrr-rL-Atrnnoreniz Enema Applicationfiled February 26, 1930, SeIiaINo. 431,556, and in-Great Britain January17, 1929.

This invention is for improvements in or relating to swash-plate rotaryengines, the term including-pumps, blowers, meters, mo tors and thelike.

Engines of this kind takevarious forms. They essentially, however,comprise a plurality of pistons arranged in a ring with their axesparallel. The-pistons are operated in their cylinders by the cam actionvuponthem of a plate (termed the swash-plate) which interceptsthe axesof. the several .pistonsat anangle, In some. engines the swash-platerotates in relation to the pistons, the cylinders beingstationary. Inothers the cylinders rotate and the swash-plate is stationary.

In eithercase it is aquestion of-cam action of theswash-plate upon thepistons, and,,as will be appreciated, the form of-bearing employed, asbetween the pistons and swashplate, is-of first importance, especiallyin the case of engines which have to operate against high pressure or athigh speeds.

In certain known forms, of swash-plateengines the pistons have engagedthe rotating 1 swaslrplate through the medium of connects ing rodsball-jointed at thetop of a thrustrace interposed between: them andtheswash-v plate. This construction, however, is eXpen-j sivetomanufacture and it calls for much lu brication. Moreover, thepermissible load at high speeds is not sufficiently high for manypurposes.

Inother known forms of swash-plate engines, the pistons themselvesengage the swash-plate, hearing at their outer ends upon a thrust-race,which in turn bears-upon the swash plate through the mediumof ballorrolling-bearings, the thrust-race being inter posed in a plane parallelto the swashplate and between it and the piston ends. The pistons areheld up to thethrust-race by a retaining member (e. g; a spider) pivotedbe tween the pistons and extending "radially from its pivot intoengagementwith each of them. It is. toengines of this particular typethe ball;

, tons and theth-rustrace.

beaiing mounted inthe end ofthepiston and comprising a spherical ballrollable within a spherical cupshaped ball-racenpon 9. s

ring ofjballs freely rollablein the race under With this form'ofbearing, friction as between the pistons-and the swash-plate, is verygreatly reduced as compared with other forms. ofbearing. [In thisconnection, it

should bepointed out that as thecylinder block and thrust-:race rotatein relation to. the

fixed swash-plate, oraccording to. the alter:

spherical. race in which theyare mounted, the

tracing out/of said circular paths does not involve rubbing. contact asbetween the. pis- The presentinvention comprises animprovement-uin ormodification of the invention ofrmy. said prior application whichconsists in providingyin respectofyeach piston, in rotarysWash-plateengines of'the type described, a ball-hearing interposedbetween the swashrplate thrust-race and the piston and comprisingaball-race the bearing-sure face of which is spherical, which ball-raceis carried on the thrust-race, an intermediate bearingrelement (e. g. aspherical ball.) interposed between said ball-race and the piston andhaving. atone side aspherical bearings surface opposed to and concentricwith the ball-race, 'balls working between the two bearing-surfaces andtwo further opposed bearing-surfaces, one on the other side oftheintermediate bearing-element and the other on the piston, of such shapethat the relative movement of the two surfaces is that of rollingcontact.

According to a further feature of the invention, that surface of thebearing-element which is opposed to the bearing-surface on the piston isspherical and concentric with the other bearing-surface of thebearing-element, and the bearing-surface on the piston is a planesurface perpendicular to the axis of the piston. This" particularconstruction ensures that the thrust transmitted to the piston from theswash-plate is directed along a line which isco-incident with, orparallel to, the axis of the piston. A lateral component of this thrustis thereby avoided, and, in consequence, friction on the cylinder wallsfrom this cause is eliminated.

A preferred construction is one in which the intermediatebearing-element is constituted by a plain spherical ball cradled at oneside in a ring of ball-bearings workingjin a concave spherical ball-racecarried by the swash-plate thrust-race, and hearing at the othersideupon a plane surface provided on the piston-end in a plane perpendicularto the axis of the piston. It is to be understood,

' however, that the invention is not limited to this particular form ofparts. For example,

' the bearing-element could take the form of a bowl having concentricspherical internal and external surfaces, in which event the externalsurface of the bowl would bear upon a plane bearing-surface on thepiston-end, and the internal surface would roll upon a ring ofball-bearings interposed between it and a convex spherical ball-racecarried on the thrust-race and concentric with the internal and externalspherical surfaces of the bearing-element. I

The invention is illustrated by way of example in the accompanyingdrawings of which-- Figure 1 is a vertical section through the end ofone of the pistons of a swash-plate engine embodying the improvedbearing of the invention as between the piston-end and the swash-plateof the engine, and

Figure 2 is a second vertical section showing an alternative form of thebearing.

Like reference characters indicate like parts in the two figures on thedrawings.

The general design of the engine is similar to that of the enginedescribed in the parent application No. 274,888. Briefly, the enginecomprises a rotary cylinder-block in which there are six cylindersequally spaced in a circle which is concentric with the axis of thecylinder-block, the several cylinders being parallel to one another andto the axis of rotation of the cylinder-block. In each cylinder is apiston the outer end of which bears against the rotating race of aninclined thrust-block. The said race is rotatable in a plane which isinclined to the direction of the axes of the pistons, and consequentlyalso to the axis of rotation of the cylinder-block. The piston-ends areheld up to the rotating race by means of a spider, the centre of whichis universally jointed so as to be capable of rotating with the pistonsand cylinder block, the ends of the arms of the spider projecting intothe interior of the piston-ends and at their extremities engagingbearing projections on the underside of the piston-ends. As thecylinder-block rotates the pistons travel round with it and being heldup to the inclined thrust-race are caused to reciprocate in theircylinders. s

Referring now to the drawings accompanying this specification, thecylinder-block is marked 1, one of the pistons therein 2, the rotatinginclined thrust-race 3, and one arm of the piston-retaining spider 4.

The thrust-race 3 bears upon a fixed race 5 secured to the stationaryframework 6 of the engine.

The improved bearing of the present invention comprises a spherical ball7 bearing with point-contact upon a plane surface 8 of ahardened steelplug 9 let into the outer end of a flanged sleeve 10 fitted in the outerextremity 11 of the piston. The ball7 bears at the opposite side (thetop) upon-a ring of balls 12'freely rollable in a spherical concaveball-race 13 fixed to the face of the rotating thrust-race 3.

The centre of curvature of the spherical race 13 is co-incident with thecentre of the spherical ball 7. Consequently, as willbe appreciated, thepiston-end bears against the rotating race 13 at all times withpoint-contact; the ball 7 rolls with point-contact on the plane surface8 as the piston reciprocates and travels round with the cylinder-blockand rotating race 3, and it also rolls with point-contact upon thespherical surface of the balls 12 which in turn roll with pointcontactupon the spherical surface of the race 13. v t i Preferably, the arm 4of the piston-retaining spider engages the piston through the medium ofa yielding bearing adapted to take into account the slight variationwhich occurs, as the cylinder-block and pistons rotate, in the distancebetween the extremity of the spider where it engages and the interior ofthe piston-end and the centre of ball 7, the object being of course toinsure that the spider arm shall at all times bear upon the piston endand hold the latter properly in place against the bearing-ball 7 To thisend there may be provided, as shown, the spring-pressed plunger 14slidable in'the sleeve 10 and spring-controlled by a compression-spring15 towards the eXtremi ty of the spider arm 4, bearing, on the underside of its head 16, upon said spider arm ex tremity through the mediumof a bearing: ball 17. v

Figure '2 shows a modification in which the bearing ball 7 issubstituted by a bowl-shaped bearing element 18. The bearing element 18is formed with two spherical surfaces 19, 20 which are concentric withone another and with a hemi-spherical concave ball ra'ce 21 fixed totherotating thrust-race 3. As in the case of theball 7 the bearingelement rolls with point-contact on the plane surface 8 provided on theextremity of thepiston andalso rolls with point-contact upon thespherical surfaces of a ring of balls 12 which in turn are freelyrollable with point-contact upon the spherical surface of the race 21 inthe space between said race and the surface 20 of the bearing-element.

If desired a bearing such as has been described as between thepiston-end and the swash-plate thrust-race 8, may be provided also asbetween the end of the spider arm 4 and the interior of the piston-end.Generally, however,-the load taken at this point is considerably smallerthan the working load at the point of hearing as between the piston andthe swash-plate thrust-race. Gonsequently, where circumstances andrequirements permit, the construction is preferably one, as shown, inwhich the spider arms simply-engage the piston-ends with plain i rubbingcontact.

It is to be understood that the invention includes, in a rotaryswash-plate engine of the type hereinbefore referred to, the provision,in respect of each piston, of two parallel plane bearing-surfacesdisposed in the end of the piston in planes which are perpendicular tothe direction of reciprocation ofthe piston, of which bearing-surfacesone is yieldingly mounted .in the piston-end to move parallelto itselflongitudinally of the piston and the other is unyieldingly mounted, andtwo spherical bearing-surfaces carried one on the swash-platethrust-race and the other on the piston-retaining-m'ember and bearingrespectively, on the two parallel plane bearing-surfaces aforesaid.

Further, in a modified form of the invention, the bowl-shaped sphericalbearing-element referred to above may be mounted upon the piston-endsothat its external surface rolls upon the rotatable thrust-race of theswashplate, the said race being formed accordingly with a planebearing-surface parallel to the thrust-race and the spherical ball beingrollably mounted through the medium of a ring of ball-bearings uponaconvex ballrace carried in the piston-end. This ballrace may, ifdesired, take theoform of a sphere resting in a hardened steel cup letinto the piston-end. In this form of the invention,

moreover, the hardened steel cup may be yieldingly mounted inthepiston-end so as to :be' movable longitudinally of the piston,

fixed relatively to the piston-end and the spherical bearing-surfacewhich is engaged by "the -retaining member may be yieldingly mounted tomove inthe direction of the length of the piston.

I claim: l I11 a multi-cylinder rotary engine hav ing a plurality ofparallel cylinders, and having pistons reciprocating in said cylinders,the combination with a swash-plate inclined to the axes of thecylinders, of thrustbearing means interposed between said pistons andsaid swash-plate, means extending. into said pistons for retalning saldplstons,

thrust-bearing means and swash plate m substantial engagement, andyielding means interposed between said retaining means and each of saidpistons and exerting thrust therebetween to compensate for variationsinthe distance between said retaining means and said swash-plate.

2. In a multi-cylinder rotary engine hav 1ng a plurality of parallelcylinders, and having pistons reciprocating in said cylin-j ders, thecombination with a swash-plate inclined to the axes of the cylinders, ofthrustbearing means interposed betweensaid pistons and said swash-plate,means for retaining said pistons, thrust-bearing means and swash-platein substantial engagement,

7 and yielding means carried by each of said pistons and engaging saidretaining means a and exerting thrust between said pistons and a saidretaining means to compensate for variations in the distance betweensaid retaining means and saidswash-plate.

3. In a multi-cylinder rotary engine having a plurality of parallelcylinders, and

having pistons reciprocating in said cylinders, the combination with aswash-plate inclined to the axes of the cylinders, of thrustbearingmeans interposed between said pistons and said swash-plate, means forretain ing said pistons, thrust-bearing means and swash-plate insubstantial engagement, and a spring pressed plunger 'slidably carriedin each of said pistons and engaging said retaining means and exertingthrust between said pistons and said retaining means to compensate forvariations in the distance between said retaining means and saidswash-plate.

4C. In a multi-cylinder rotary engine havinga plurality of parallelcylinders, and

having pistons reciprocating in said cylinders, the combination with aswash-plate inclined to the axes of the cylinders, of thrustbearingmeans in line with each piston and associated with said swash-plate, asleeve inserted in one end of each of said pistons, said sleeveshaving'flat surfaces for engaging said thrust-bearing means, a springpressed element slidably supported in each of said sleeves, and a memberfor retaining said pistons and associated sleeves against saidthrust-bearing means, said member engaging said spring pressed elements.

In testimony whereof I aflix my signature.

I 10' JOHN FREDERICK NEVINSON CRAIG;

